At least three women and six children from a U.S. family have been killed in an ambush in northern Mexico, Mexico’s security minister said.

The victims were members of the LeBaron family, U.S. citizens who formed a fundamentalist Mormon community decades ago in the border region, according to Security Minister Alfonso Durazo and relatives Alex and Julian LeBaron.

The attack occurred when family members were traveling in three separate vehicles on a dirt road between the border states of Chihuahua and Sonora, several family members said.

Durazo confirmed family members were traveling in a convoy and said family members could have been confused with criminal organizations battling for control of the region.

Durazo also said police and army troops are searching for a missing child.

The killings were the latest in a string of recent attacks in Mexico that have shocked a country that is used to violence.

U.S. President Donald Trump quickly began applying more pressure on Mexican President Andres Manuel Lopez Obrador to crack down on armed drug groups.

“If Mexico needs or requests help in cleaning out these ….. monsters, the United States stands ready, willing & able to get involved and do the job quickly and effectively,” Trump tweeted.

“The great new President of Mexico has made this a big issue, but the cartels have become so large and powerful that you sometimes need an army to defeat an army!,” Trump wrote.

“This is the time for Mexico, with the help of the United States, to wage WAR on the drug cartels and wipe them off the face of the earth,” he added . “We merely await a call from your great new president!”

Shortly after Trump’s call for action, President Lopez Obrador said at a news conference he would talk with his U.S. counterpart about a cooperative response to the massacre.

“All the cooperation that is needed is what I’m going to talk to Trump about,” Lopez Obrador said.

The state governments of Chihuahua and Sonora released a joint statement saying an investigation has begun.

The statement also said federal and local security forces were being sent to an area between the two states, but did not disclose details.

U.S. Ambassador to Mexico Christopher Landau said he was monitoring the situation closely.

Two members of the Chihuahua Mormon community, including a LeBaron family member, were killed in 2010 in an apparent revenge attack after security forces tracked down drug gang members.

Prior to 2010, the Mormons in the area were subject to many kidnappings.

Mormons of Germanic origin left the U.S. and established a settlement in northern Mexico. The group broke away from the mainstream Mormon church when it abandoned polygamous marriages.